1. Field
Embodiments relate to an apparatus, method, and medium for generating an image, and more particularly, to an apparatus, method, and medium for generating an image which can generate a high-dynamic range (HDR) image using an image obtained by a single exposure.
2. Description of the Related Art
In recent years, the distribution of digital cameras and devices equipped with high-resolution cameras such as camera phones has been widespread. These cameras generally include a lens and an image sensor.
Lenses collect light reflected from an object, and image sensors detect light collected by lenses and convert the collected light into electrical image signals. Image sensors are typically solid-state image sensors. Examples of the solid-state image sensors include charge coupled device (CCD) and complementary metal oxide semiconductor (CMOS).
Image sensors of cameras may include a color filter array (CFA) having a mosaic of color filters in which each color filter filters light reaching each pixel. Since image sensors are highly sensitive to near Infra-Red (NIR) light, image sensors of cameras may also include an NIR shield filter which is mounted on a CFA for preventing image discolorations caused by NIR light.
In the case of capturing images in a high-illumination or low-illumination environment or in a sharp contrast environment with backlighting, conventional image sensors using conventional CFAs may not be able to accurately capture color images due to conventional CFAs' inherent limitations in dynamic range. As a result, the rendered image will loose information either in the shadows or in the highlights for high dynamic range (HDR) scenes.
In order to address this problem, high dynamic range (HDR) image sensors capable of accurately capturing images even in a high-illumination or low-illumination environment or in a sharp contrast environment with backlighting have been developed. However, the HDR image sensors are generally expensive sensors mainly used for precision measurement purposes or for security and military purposes and they are not suitable for consumer products due to their cost and complexity.
Conventionally, an HDR image is created by generating a plurality of images with different light exposure amounts. For example, in the case of capturing images of an object in a backlighting state, images obtained with short exposure would capture highlighted area without saturation but dark shadow areas will not be visible, whereas images obtained with long exposure may have visibility in the dark areas but may loose information in bright areas due to saturation. Therefore, HDR images can be obtained by blending the image(s) obtained with short exposure and the image(s) obtained with long exposure.
In order to obtain a long-exposure image, a user must hold the imaging device for a long time, thus compromising user convenience since it would require a tripod and stationary objects. If the position of an object changes during an image capturing operation, a long-exposure image and a short-exposure image obtained by image capturing operation may not be the same, thereby making it difficult to properly generate an HDR image. Also, a user may accidentally shake his/her hand by holding the imaging device for a long time and may thus produce blurred images.
Japanese Patent Laid-Open Publication No. 2006-211478 discloses a method of generating an HDR image from images in which an exposure time is varied according to the sensitivity of filters by appropriately arranging primary color filters with low sensitivity and complementary color filters with high sensitivity. This method, however, may result in blurry images due to a shake in a user's hand during an exposure time and may not improve sensitivity considerably.